Can extended Chaplygin gas source a Hubble tension resolved emergent universe ? (2307.02602v2)

Abstract: In this paper, we attempt to explore the possibility of a obtaining a viable emergent universe scenario supported by a type of fluid known as the extended Chaplygin gas, which extends a modification to the equation of state of the well known modified Chaplygin gas by considering additional higher order barotropic fluid terms. We consider quadratic modification only. Such a fluid is capable of explaining the present cosmic acceleration and is a possible dark energy candidate. We construct a theoretical model of the emergent universe assuming it is constituted from such a fluid. It interestingly turns out that the theoretical constraints we obtain on the extended Chaplygin gas parameters from our emergent universe model are well in agreement with the observational constraint on these parameters from BICEP2 data. Our model is found to replicate the late time behaviour really well and reproduces $\Lambda$-CDM like behaviour, as evident from the analysis of the statefinder parameters. Moreover, the Hubble parameter analysis shows that for theoretically constrained values of the ECG parameters, the Hubble tension can be resolved yielding higher values of the present Hubble parameter $H_0$ in all possible cases. Also, the value of $H(z)$ at a redshift $z=2.34$ fits better than $\Lambda-CDM$ with recent observations in some cases. This leads us to the realization that such a fluid is not only a probable candidate for dark energy, but also sources an emergent universe unlike modified Chaplygin gas and the initial singularity problem can be resolved in a flat universe within the standard relativistic context.